Whole Lung Irradiation in Rhabdomyosarcoma With Lung Metastases: A Report From the Soft Tissue Sarcoma Committee of the Children's Oncology Group.

Purpose: Patients with rhabdomyosarcoma with metastatic disease have a poor prognosis despite therapy intensification. The aim of this study was to investigate the efficacy of whole lung irradiation (WLI) in patients with rhabdomyosarcoma and lung metastases.
Methods: Patients with rhabdomyosarcoma with lung metastases enrolled on four Children's Oncology Group protocols (D9802, D9803, ARST08P1, ARST0431) were retrospectively reviewed. Event-free survival (EFS) and overall survival (OS) were compared between patients who received and did not receive WLI.
Results: In 143 patients with rhabdomyosarcoma with lung metastases, 65 patients (45.5%) received WLI and 78 patients (54.5%) did not receive WLI despite protocol requirements. The 5-year EFS was 38.3% (95% CI, 24.8 to 51.8) in patients who received WLI and 25.2% (95% CI, 13.8 to 36.6) in patients who did not receive WLI ( P = .0496). The 5-year OS was 45.5% (95% CI, 31.8 to 59.3) in patients who received WLI and 32.4% (95% CI, 20.4 to 44.4) in patients who did not receive WLI ( P = .08). In exploratory subgroup analyses, the benefit of WLI on EFS and OS was significant in patients 10 years and older. Other clinical factors associated with EFS on univariable analysis included age, histology FOXO1 fusion status, number of metastatic sites, location of metastatic sites, and Oberlin Score.
Conclusion: WLI is associated with improved EFS in patients with rhabdomyosarcoma with lung metastases. These results highlight the potential importance of WLI and need for more stringent protocol compliance for administering WLI.